1. Field of the Invention
The present invention relates to an LED (Light-Emitting Diode) output power adjusting device and a method thereof, and in particular to a device that controls the output power of an LED based load through detection of a forward voltage and a computation and evaluation process and a method thereof.
2. The Related Arts
An LED (Light-Emitting Diode) is a light source device, which emits light when being applied with a sufficient current across opposite ends thereof. However, an LED induces a forward voltage that is not a constant and may change with the variation of temperature or environmental factors. Thus, the output power of the LED is not of a constant power condition and may change with the variation of temperature and environmental factors.
Further, electrical loading formed of an LED lighting device that is constituted by composing a plurality of LEDs in the form of an array or lighting strips may not be capable of controlling variation of output power that is caused by the variation of the LEDs induced by change of temperature or environmental factors. Thus, an estimation process is often performed to ensure a desired output power. This is often done through “burning” of the lighting device, wherein the LED lighting device is put into operation for quite a period of time and then the output power of the lighting device is measured from which the output power of an actual operation of the lighting device is inferred. However, since an LED has an extensively long lifespan, the conventional way of burning, which is carried out for only a relatively short period of time, is not very precise in predicting the actual output power of the lighting device. Thus, significant errors are often found for the output current of which prediction and estimation are done through device burning so that the output power of the lighting device cannot be precisely controlled, making it difficult for the lighting device to operate with reduced power consumption.
Further, the known LED lighting devices often suffers constant change of output power caused by unstable forward voltage due to vibration of temperature. Thus, the conventional LED lighting devices must be tested with device burning on such an extent that the forward voltage of the LED get stable before a constant current power supply of an actual output be set and output power being controlled. This takes a large amount of valuable working hours and human labor, and thus leading to drawbacks of power throughput of LED lighting device manufacturing and high costs. Further, to ensure output power of a manufactured LED lighting device, a large rating power must be set in order to handle any insufficiency of output power after the lighting device has shipped to a user. This makes the conventional LED lighting devices not complying with the requirement of low power consumption for environmental conservation.
Various techniques in this respect are available, such as Taiwan Utility Model M350199 that provides a control system for extending lifespan of LED lighting, in which two set of LED lighting string are lit alternately to cope with the problem of temperature variation. However, device burning must be carried out in order to set the output power of the LED lighting strings. Further, this conventional arrangement requires two sets of LED lighting strings, which unnecessarily adds the manufacturing costs.